Haven't seen this problem come through the forum yet, but it has been posted on others. Thought I'd share my troubleshooting:
Over the last month or so, what can be described as a whine or howl had developed, most noticeable on the highway - While in gear and throttle is applied (at any speed or in any gear). If clutch depressed, only regular engine noise is heard (Not an RPM related noise).
Had it in for service (while my powertrain warranty was still effective) last week, and a worn output bearing was the culprit. Tech indicated that it was likely due to a high spot in the bearing and it has slowly worn over time. I have a few pictures of the part that I will post if there is interest.
2.4L 5 speed for the record - 98 700km
Now to address my squeaky rear struts
(and yep.. i've replaced everything but the struts in the rear...)